The influence of the additions of B and P on the cellular and intragranular precipitation in Ni-8–15 mass%Sn and Cu-80 mass%Ni-8 mass%Sn alloys was investigated by quantitative metalographic methods.
By the additions of B and P, the intragranular precipitation was slightly retarded, while the cellular precipitation was significantly suppressed. The suppressing effects of B and P depended upon the Ni concentration in the Cu–Ni–Sn alloys and were especially large in the 40–60%Ni alloys. These effects increased with increasing amount of addition. It is considered that B and P segregate in the grain boundaries and suppress the nucleation and growth of cells.